What is meant by a linearly polarised light? Which type of waves can be polarised? Briefly explain a method for producing polarised light. Two polaroids are placed at `90^(@)` to each other and the intensity of transmitted light is zero. What will be the intensity of transmitted light when one more polariod is placed between these two bisecting the angle between them ? Take intensity of unpolarised light as `l_(0)`

Explanation

A light wave is said to be linearly polarised if its electric field vector vibrates just in one direction perpendicular to the direction of propagation. Only tranverse waves can be polarised. Light can be polarised by reflecting it from a transparent medium. The extent of polarisation depends on the angle of incident. At a particualr angle of incidence, called Brewster angle, the reflected light is completely polarised as shown below :

Numerical : `l=l_(0) cos^(2) theta=l_(0)xx((1)/(sqrt2))^(2)=(I_(0))/(2)`
Resultant intensity `l_(R)=l cos^(2) theta=l_(0)(I_(0))/(2)xx((1)/(sqrt2))^(2)=(I_(0))/(4)`